Array changing doesnt work

Question

Array doesn't change after running this code. What is the reason of it? Thank you

 Scanner s = new Scanner(System.in);
 String [] h = new String[100];
 int hlds = 0;
 while (true) {
 System.out.print("Enter: ");
 if(s.hasNextLine()) {
 String str = s.nextLine();
 if (Pattern.matches("[abc]", str)) {
 h[hlds++] = str;
 }
 for( int i = 0; i < h.length ; i++){
 System.out.println(h[i]);
 }
 break;
 }

• Yanki Twizzy: What are you trying to achieve with this code?
• iwazovsky: I need to write down strings in array , which contain letters abc
• Maroun: Probably because if (Pattern.matches("[abc]", str)) is never met.
• iwazovsky: So, how i need to change it?
• MrSimpleMind: I have updated my answer, so you want strings which contains letter a, b, or c in the input line.

Answer 1

Pattern.matches("[abc]", str)

Evaluates to true only if you enter either a or b or c

because of the regex you have used [abc], see the docs about regular expressions

If you enter ab then it would not be accepted.

If you want your input to contain any of the char then you could change your regex to [abc]+.

Answer 2

Your regex [abc] means "a single character either a, b or c".

Change your regex to [abc]+, meaning "one or more characters either a, b or c"

Answer 3

Extra Info:
This would also work:

str.matches("[abc]+");

It calls Pattern.matches(regex,this); internally. (where regex is the regular expression used)

Answer 4

(updated after reading all comments...)

Okey, so if I understand it right: You want to store into the array from input line those who contains a, b or c letters.

apple, ball, catch, table, tictac... will be stored. Right?

I would use the String contains, or indexof to fins a, b, and c letters. This is more efficient that regex.

Scanner s = new Scanner(System.in);
String [] h = new String[10];
Pattern p = Pattern.compile("(a|b|c)");
for(int hlds=0; hlds<h.length;hlds++ ) {
 System.out.print("Enter: ");
 String str = s.nextLine();
 /* with regex
 if( p.matcher(str).find() ) {
 h[hlds] = str;
 }
 */
 /* with contains */
 if( str.contains("a") || str.contains("b") || str.contains("c") ) {
 h[hlds] = str;
 }
}
System.out.println(Arrays.toString(h));

• A4L: The loop is ok, but OP wants strings that match a pattern, not that all are equal to abc and ending with an array of 100 abcs.
• iwazovsky: No. I'm just trying to find strings, which contain a, b or c and write them down to an array.